Support the essential part of Shadow DOM v1

third_party/WebKit/Source/core/dom/shadow/SlotAssignment.h

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef SlotAssignment_h
+#define SlotAssignment_h
+
+#include "platform/heap/Handle.h"
+
+namespace blink {
+
+class HTMLSlotElement;
+class Node;
+class ShadowRoot;
+
+class SlotAssignment final {
+public:
+    SlotAssignment() { }
+    HTMLSlotElement* assignedSlotFor(const Node&) const;
+    void resolveAssignment(const ShadowRoot&);
+
+    DECLARE_TRACE();
+
+private:
+    void assign(Node&, HTMLSlotElement&);
+    WillBeHeapHashMap<RawPtrWillBeMember<Node>, RawPtrWillBeMember<HTMLSlotElement>> m_assignment;
+};
+
+} // namespace blink
+
+#endif // HTMLSlotAssignment_h